1. Field of the Invention
This invention relates to a device for measurement of electrostatic potential on a body, and particularly a device of such type which does not require a ground connection.
2. Description of the Related Art
Electrostatic Field meters have been used for at least 30 years. These meters are available in a variety of shapes, configurations, and range capabilities. The principle of operation also varies widely. The most famous technologies include: electro-mechanical meters, electro-optical meters, radioactive-source meters, and electronic meters.
The electronic field meter is the type most commonly used today, due to its simplicity and low price. The electronic field meter became possible with the advances in semiconductor technology, and particularly with the appearance of the field-effect transistor (FET). The circuit widely used by manufactures of electronic field meters comprises at least one FET, and associated circuitry for generating a voltage proportional to the field intensity at the gate of the FET.
While electronic field meters have been useful for measurement of electrostatic fields in a variety of applications, they generally suffer from one common disadvantage: the field meter must be held at a relatively large distance from the charged object. This is necessary to protect both the instrument and the operator from spark-over which may result from an object charged to a high potential. Further, since the potential on any charged object is not known as a priori, the operator must generally perform guesswork to determine the proper distance at which the field meter should be held.
A further complication occurs when the object under test has an irregular geometry (shape). Generally, if the object under test does not have a large, regularly shaped planar surface, then the reading of most field meters used today is extremely inaccurate. Considerable accuracy may be obtained by utilizing a ground connection to establish a reference potential; however, such ground connection is usually inconvenient to the user.
It is the objective of the present invention to provide a device which will allow the measurement of extremely high voltages on any charged body, without the risk of exposing the operator to such high voltages; mainly by allowing the meter to be mounted directly on the object under test and be observed by the operator from a safe distance.
It is another objective of the present invention to provide a device which will take accurate measurements of electrostatic potentials in a manner that is independent of the geometry of the object under test, without utilizing a ground connection.
Other aspects and features of the invention will be more fully apparent from the ensuing disclosure and appended claims.